The present invention relates to a process for determining the torque transmitted by gas forces to the crankshaft of an internal-combustion engine by analyzing the rotational speed data, and, more particularly, to a process which detects the rotational speed data by determining rotating speed of a component fixedly connected with an engine crankshaft, the rotating moment being computed by the inertia moment of the engine from the angular speed correlated with the rotational speed.
DE-OS 40 40 648 describes a process for a non-test-bench determination of characteristic technical values of internal-combustion engines and their individual cylinders. The rotational speed, the rotational moment, the work and the power of the internal-combustion engine or of individual cylinders of the internal-combustion engine, are determined by detecting the rotating movement of the crankshaft. A disadvantage of this process is that the torques which result from the acceleration of the pistons and oscillating mass components of the connecting rods and from the crankshaft torsion are not taken into account.
The use of electronic engine controls for diesel and Otto engines is becoming increasingly important. Unfortunately, the resulting advantages with respect to consumption and exhaust gas have been counteracted by unsolved problems in the precise quantitative proportioning because of high component tolerances and aging-related drifts. Intensive efforts to maintain increasingly smaller tolerances and to improve long-term stability of magnetic valves and other components relevant to the quantitative proportioning can be reduced almost to zero by the use of an engine regulating system. So far, however, no low-cost process which can be used in series production has been available for recognizing such tolerance-caused cylinder-specific output differences.
It is an object of the present invention to provide a process by way of which the torque, which is transmitted from the pistons by the connecting rods to the crankshaft and which results from the gas pressures in the cylinders, can be determined from the rotational speed signal.
This object has been achieved in accordance with the present invention by a process which uses an engine model to compute torque of oscillating masses, moments from the crankshaft torsion and static torque composed of all slowly variable friction moments, effective moments and load moments, determines torque from these torques and moments, resulting from gas pressures in engine cylinders, and supplies the resulting torque to a control system and/or a diagnostic system for the engine.
By taking into account the torques of the oscillating masses, the torsional moments of the crankshaft and the static torques, the torque which is transmitted from the pistons by the connecting rod to the crankshaft and which results from the gas pressures in the cylinders is determinable. From this quantity, the work which is carried out by the individual cylinders per working cycle or other operating parameters correlated with this torque can then be determined and supplied to the engine control or the on-board diagnostic system.
In order to reduce the computing power requirements of the analysis unit, the torsional moments occurring in the normal operation are preferably first computed once and then stored in a characteristic diagram. It is further advantageous for the use in engine control to store, the corresponding derived effects of the torsional moments on a control quantity of the engine control, instead of the torsional moments, in a characteristic diagram.
By way of a precise rotational speed measurement and by a detailed engine model, the process according to the present invention now provides a control quantity for the identification of the cylinder-specific output. By way of these quantities derived from the rotational speed, a control device for the compensation of differences caused by manufacturing and aging can be implemented with respect to each cylinder in the entire characteristic engine diagram. As a result, the rotational speed and the quantities derived therefrom, such as the angles of rotation, the angular speed and the angular acceleration, are the only quantities required for computing the work delivered per cylinder and working cycle, or the corresponding control quantity.